Tolkien may have written a lot but not particularly well, but for some reason, many fantasy writers insist on regurgitating his ideas. This forum is for people who like really innovative fantasy, like China Mieville's Perdido Street Station.

Has anyone out there tried to create their own unique world? Not a simple world that just has different nations and boundaries from other fantasy realms, but something wholly and fundamentally different?

I have done it several times. There's a realm of ideologies made manifest in my own "Hallowed Be The Fatherland," and an attempt at a hard sci-fi multiverse in my "In The Eyes of God." My earlier novel "Shores of Eternity" takes place outside of time, in a location where things 'removed' from the timeline end up. A similar, harder scifi setting is here:
Some good works to look at for innovative worldbuilding are China Mieville's "Perdido Street Station," "The Scar," "Iron Council," and Frank Herbert's "Dune" series. Likewise, some "inventive" settings I've seen are Paul MacAuley's Confluence series (takes place on a continent sized orbital platform with its own atmosphere), Armada in "The Scar" (a city-state made of several tied together ships), Discworld, a parody of fantasy created by Terry Pratchet, and Ringworld (a massive ring around a star made habitable by supertechnology, and clear inspiration for "Halo").
Likewise, there's Gene Wolfe's Book of the New Sun, which takes place on an Earth with ancient tech so advanced, its indistinguishable from magic.

Yeah, I know about those listed in the second paragraph. I absolutely love "Dune," it's one of my favorite sci-fi works of all time. I was mainly asking more for stuff made by people here. I'll be sure to check out yours. I'm trying to decide whether or not to upload mine; I never wrote more than one chapter in it, but I love the setting. I think I could do a lot with it if I ever sat down and made myself work on it some more.

Original fantasy world? Are you telling me there's another way? ...Heh. The answer is, yes, of course I make my own fantasy worlds.
And to answer that little question floating around your brain ("how?") I warp human history. A. Whole. Darn. Lot.
Take the world of my story, The Oracle of Yet to Be. Its backstory is very loosely based on the revolutions of the 18th century. If the 13 colonies had been 13 isles stretched between the tropics and the subarctic, if the Americans had been close enough to that tiny island nation of a mother country to hop over and behead their king, if the Articles of Confederation had never been abandoned, if the 13 colonies had been a hell of a lot more ethnically diverse, and if you would fast forward five hundred years, you would have my world--the part of it used in the story, anyway. There's also an invading naval fleet coming their way eventually (think Cortez vs. Aztecs with the resources, the survivors, and the power structure to launch a counterattack).
Another way that I purposefully deviate from Tolkienesque, D&D, and traditional faux-medieval fantasy is that the story is very subtle in its magical and supernatural aspects. Superstitions and a belief structure are definitely there, as are an alarming number of coincidences, but the only tangible proof of otherworldliness is the existence of the Oracle of Yet to Be, a powerful seer who, for a miracle (at least in fantasy fiction), is actually semi-sane.
To make up for the nearly magicless desert I've created, I load the story with a vibrant culture and make it a point to lampoon story cliches when possible and avoid doing the usual. For just one example, just to shake things up, I decided to have caucasians be considered a sort of rare exotic breed, as they inhabit only parts of the two southernmost isles. Only one major character and very few minor ones really can be classified as 'white.'
On a final note, I'm really having a lot of fun with this piece, most likely because breaking free of the mold lets me take it in any direction I want. And I can't tell you how cool it is not to be landlocked and have to worry about fiefdoms and border disputes (gag!).

For me, combining history with some ideas of my own can work. For instance, I'm trying to develop the world for Hymn of Steel and Might 'organically.' That means I start with evolutionary biology for each continent, work out the resources available, and what kind of societies would develop based on those resources. Then, if I want to use any Earth-based inspirations for cultures (Polynesian, Indian, etc.), I research a bit into them and warp any history and mythology for the setting. If I'm using something original (IE an original human culture), I'll improvise a lot of it. Society types I avoid like the plague are Arthurian-British and feudal Japanese. For now, I'm enjoying Chinese, Roman/Byzantine, Brazilian (as in the form of an ethnically diverse society with vaguely Portugese names), Irish (Irish steampunk rather than fairy-tale Celtic BS), and Polynesian inspirations for cultures. Heck, I've been wanting to do something relating to Mongolians for a long time.
In my stories, the supernatural often takes the form of a science. Thaumaturgy is merely a form of physics (an inconsistent one, but enough of a constant one it can be mass produced). The user's belief also factors into it. Using my thermodynamics textbook, I've come up with a few equations to describe it, even a unit (1 thaum is the amount of concentration needed to move a 1 Newton object 1 meter within 1 second). I'm renaming the metric units a bit, and the theory will be described by two of the main characters, who are differnt sorts of engineers. In addition to mechanical and structural engineering, there's also "thaumechanical" engineering. The reason electronics have stagnated in the setting is widespread use of thaumechanical steampunk. Thaum-electronics is much more cost prohibitive. Economics also plays a large part, believe it or not...

Well, Monev it worked for Clarke and Rama :p
But I have to say that "scientific" magic is great, when pulled off properly. It's too much of a deus ex machina, usually, when it's just some wonderful ineffable force that solves all problems: when it has limits (just like any other force of nature), it becomes much more believable and... well... *fun* to read about!

[q]Well, if mass production is harder, then there's one factor right there.[/q]
When you say this, do you mean that, when magic is being used, it takes more effort to make a lot at once...or that it's more difficult create or manipulate something larger? Like the first thing JK Rowling's Transfiguration students learn is to turn a match into a needle and they later move onto larger object and more complex changes?
...I know you guys are railing on me for using Harry Potter, but I figure more people will know what I'm talking about, especially the younger set, and I like to use the world as a diving board for my earth-fantasy work...not that I use magical schools, or even wizardry. Truth is, it's so vague and there are so many things left to the imagination that it's an easy matter to choose a large, murky area, fill it in my own way, wrest it from the HP copyright's grubby hands, and run with it. I've come up with an Underworld (beneath the law) run by goblins, trolls, minotaurs, and such. I've come up with a story where the characters of Arthurian Legend are mixed up in a war against 'the gods,' an elder, magic-wielding race. I've come up with an idea where the newest incarnation of the god Loki is unlucky enough to have the Ragnarök prophecy (in which she is fated to die) start to come true, and so she beings a quest to derail it and in doing so save the world from Apocalypse (try arguing I stole THAT from JKR).
True, this forum is about original world fantasy, but ancient and futuristic earth-fantasy pieces are valid options for escaping reality as well. And there's no reason you can't mix and match. I recall that some of Mercedes Lackey's non-Valdemar work manages to be Urban fantasy and High fantasy and something I can only describe as a Magical Acid Trip by using both the idea of Underhill (a world beneath) and multiple dimensions.

Ever read Neil Gaiman's "American Gods?" Great book. It basically is a combo of high and urban fantasy, as the old gods (Norse and Egyptian, etc.) battle the new ones (Television, Money, etc). Fun stuff. What I mean by mass production is how magic or supernatural items are produced. Is there some sort of magic factory? Is it cost-prohibitive or require years of training to conjure something out of nothing? Industrial fantasy does make for some interesting thoughts. I portray arcane industries as run by physics more fickle than quantum mechanics, so it requires years of training to understand and comprehend. Far more often, people just mass produce what works without knowing how it works.

[q]Ever read Neil Gaiman's "American Gods?"[/q]
No, but I'm thinking that I will. It sounds sort of like my favorite fantasy premise: "Human belief is the life's blood of the supernatural." Basically, supernatural creatures must be believed in to continue to exist, as must sentient magical beings like Sirens and gods, but for them it's more than instinctual feeding; like they say, Everyone is selling something. Throw in the possibility of spiritual turf wars, business conglomerates, dictatorships, and door-to-door salesmen...and I think you get the picture.
[q]Is there some sort of magic factory? [/q]
...Great, now I have the urge to watch Shrek 2 again.

I also intend to read American Gods. If you're going to use 'conjuring something out of nothing' it might be best to revive Larry Nivan's (the author of Ringworld) premise that mana can be depleted like any natural resource.